Niu Peng-Ju, Wei Shi-Yong, Fang Dun, Dan You-Meng
Department of Chemistry and Environmental Engineering, Hubei University for Nationalities, Enshi 445000, China.
Key Laboratory of Biologic Resources Protection and Utilization of Hubei Province, Hubei University for Nationalities, Enshi 445000, China.
Huan Jing Ke Xue. 2016 Jun 8;37(6):2220-2228. doi: 10.13227/j.hjkx.2016.06.027.
In this study, the binary systems of kaolinite-goethite mixture (KGM) and kaolinite-goethite complex (KGC) were prepared by different methods, and the surface properties and humic acid adsorption of the samples were investigated. Results showed that the specific surface area (SSA) of the samples followed the order of goethite> KGC> KGM> kaolinite, and the SSAs increased significantly for KGC while slightly for KGM when compared to the average value of kaolinite and goethite. The isoelectric point (IEP) of kaolinite, goethite, KGM and KGC appeared around 3.2, 7.9, 6.1 and 6.7, and the Zeta potential at pH 5.0 was -13.9, 38.2, 14.3 and 19.7 mV, respectively. The adsorption kinetic data for humic acid were well fitted using the pseudo-second-order kinetic models, suggesting that chemisorption was important in the adsorption process. Both one-site and two-site Langmuir models were suitable to describe the isotherm adsorption data (R2 0.962-0.993), and the correlation coefficients of two-site model for the binary systems were relatively higher (R2>0.989). The R2 values of Freundlich model fiting the adsorption data were low for the four samples, especially for the two pure samples. This indicated that the adsorption with various sites and mono-layer model was important in adsorbing humic acid onto the binary systems. At the initial pH of 5.0, the adsorption capacity (q) of kaolinite, goethite, KGM and KGC was 6.02, 61.83, 35.13 and 42.10 mg·g-1, respectively. The q values of KGC and KGM increased to different extents when compared to the average of kaolinite and goethite. Thermodynamic parameters indicated that the adsorption of humic acid were endothermic for the four samples and non-spontaneous for kaolinite while spontaneous for the other samples.
在本研究中，通过不同方法制备了高岭石-针铁矿混合物（KGM）和高岭石-针铁矿复合体（KGC）的二元体系，并对样品的表面性质和腐殖酸吸附性能进行了研究。结果表明，样品的比表面积（SSA）顺序为针铁矿>KGC>KGM>高岭石，与高岭石和针铁矿的平均值相比，KGC的SSA显著增加，而KGM的SSA略有增加。高岭石、针铁矿、KGM和KGC的等电点（IEP）分别出现在3.2、7.9、6.1和6.7左右，在pH 5.0时的Zeta电位分别为-13.9、38.2、14.3和19.7 mV。腐殖酸的吸附动力学数据用伪二级动力学模型拟合良好，表明化学吸附在吸附过程中起重要作用。单位点和两位点Langmuir模型均适用于描述等温吸附数据（R² 0.962 - 0.993），二元体系的两位点模型相关系数相对较高（R²>0.989）。Freundlich模型拟合吸附数据的R²值对四个样品均较低，尤其是对两个纯样品。这表明具有不同位点的吸附和单层模型在二元体系吸附腐殖酸过程中起重要作用。在初始pH为5.0时，高岭石、针铁矿、KGM和KGC的吸附容量（q）分别为6.02、61.83、35.13和42.10 mg·g⁻¹。与高岭石和针铁矿的平均值相比，KGC和KGM的q值有不同程度的增加。热力学参数表明，四个样品对腐殖酸的吸附均为吸热过程，高岭石的吸附为非自发过程，而其他样品的吸附为自发过程。
